Ralph -
Many - not all - fluorescent lamps (I am assuming you are talking a
CFL , or Compact Fluorescent Lamp) have a small resistor used as a fuse
for the ballast. The ballast is in the base which supports the
discharge tube (the fluorescent portion). The ballast develops the
voltages needed to initially fire the tube (when cold) and limit the
current once the arc is initiated. It consists of several capacitors
and resistors as well as a few semiconductors. As the tube ages, the
current draw increases. At some point, it becomes too much, and the
ballast fails. To prevent a really catastrophic failure, a small
resistor (typically a 1/8 or 1/4 watt unit) is used as a fuse. Overload
destroys the resistor, cutting off the current. Why a resistor? They
are much less expensive than fuses, particularly at low current
ratings! The light from a CFL comes from a mercury-vapor arc inside the
tube, which emits large amounts of ultraviolet light. The phosphor on
the inside of the tube converts the ultraviolet energy into visible light.
- Jim, KL7CC
Ralph Tyrrell wrote:
As I sit at my computer the radio desk is to my back. I heard a burst of static
behind me. That was odd since no radios were on. The only thing on at the
radio desk was the desk lamp and a power supply that keeps the batteries
charged. Both are plugged into a strip that switches power to them.
I went over to the radio desk and looked at my equipment, both off. Still
puzzled I turned on the 2m rig, all normal. Then I turned on the K3. All
normal. I turned them off again. The K1 sits by, not connected to anything at
this time.
Still puzzled I sat there wondering if something had happened to my battery
bank or one of the batteries. I have three 26AH batteries in parallel. Each
battery is fused before to goes to a fused buss.
Then my nose began to notice the smell we all dread. Something electrical was over heated. Still I did not noticed a symptom I should have noticed earlier, the desk lamp was off. I touched the top of the lamp and it was very hot. The bulb, a 13 Watt Florissant had failed. The ceramic base was too hot to touch.
How often do Florissant bulbs fail this way?
I had the feeling that if I were not there a fire may have started.
73, Ty, W1TF, K3 #696, K1 #1423
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